Document FR-A-2 614 969 describes an indicating light unit comprising a single light source, a light processing or flux recovery and distributor mechanism relatively close to and surrounding the bulb, and a generally flat glass or lens.
The flux recovery and distributor mechanism is designed to modify the homogeneous angular distribution of the light emitted by the bulb all around it into a homogeneous distribution of the light, in linear terms, along at least one direction of the lens.
The lens comprises optical members in the form of striations defining steps of a cylindrical Fresnel lens, for example, designed to redirect the light from the flux recovery and distributor mechanism towards the required signaling area, generally determined by regulations.
Accordingly, the above prior art indicating light unit has a more homogeneous distribution of the light leaving the lens than a light unit with no such flux recovery and distributor mechanism, because the areas of the lens closest to the bulb in a light unit without a flux recovery and distributor mechanism receive a significantly greater quantity of light per unit surface area than areas of the lens further from the bulb.
However, the indicating light unit according to FR-A-2 614 969 has the required homogeneity properties only if the lens is substantially flat. There is nothing in the above document to indicate or to suggest how to deal with the situation in which the lens is curved, which is more and more frequently required in modem motor vehicles.
What is more, it is apparent that the striations formed on the lens can have greatly varying light transmission coefficients, according to the deflection that they are required to provide.
This also contributes to the homogeneity of a prior art indicating light unit of the type with a flux recovery and distributor mechanism being less than perfect, despite the effect of the flux recovery and distributor mechanism.